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Reference Specification
for
Next Generation Networks (NGN) Technical Framework
IDA RS NGN Tech Framework Issue 1, February 2007
Info-Communications Development Authority of Singapore Resource
Management & Standards 8 Temasek Boulevard #14-00 Suntec Tower
Three Singapore 038988 Copyright of IDA, 2007 This document may be
downloaded from the IDA website at http://www.ida.gov.sg and shall
not be distributed without written permission from IDA
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Contents
Page 1 Scope
3
2 NGN Architecture Overview
4
3 NGN Functions
6
3.1 Transport Layer Functions
6
3.2 Service Layer Functions
8
3.3 End-User Functions
8
3.4 Management Functions
8
4 NGN Functional Entities
10
5 NGN Service-specific Components
12
6 Security Considerations
13
7 NGN Release 1 Services
14
8 Capability Requirements for NGN Release 1
16
9 References
17
This Reference Specification is a living document which is
subject to review and revision. Reference Specifications and Guides
are informative documents and are not used for approval of customer
equipment. They are either one of the following types of documents:
i Informative and interim documents on customer equipment
standards which are yet to be adopted by network operators, and
where standardisation is still in progress.
ii Informative documents describing network standards adopted by
the
public telecommunication networks in Singapore.
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1 Scope 1.1 This Reference Specification outlines the technical
framework which is relevant
for developing the Next Generation Networks (NGN). It refers to
the architecture for NGN given in the ITU-T recommendation for
Functional Requirements and Architecture of the NGN for Release 1
(ITU-T Rec. Y.2012).
1.2 The architecture for NGN shown in section 2 of this
Specification is a functional
architecture where a set of functions is used to describe the
NGN structure. Each function is defined and specified as a set of
functional entities (outlined in sections 3 and 4 of this
Specification). Groupings of functional entities are used to
describe the physical NGN implementations, and determine the
capabilities supported in the NGN. Therefore network operators may
choose and combine the functional entities according to their
business models, services and capabilities to be supported.
1.3 NGN service-specific components required for the NGN to
support services such
as the mediated multimedia services and the PSTN/ISDN service
capabilities are outlined in section 5 of this Specification.
Security considerations are defined in section 6 of this
Specification.
1.4 This architecture for NGN allows for the support of services
identified in the ITU-T
Y series Supplement 1 for the NGN Release 1 scope, which are
outlined in section 7 of this Specification. It also allows for the
support of capabilities and capability requirements identified in
the ITU-T recommendation for the NGN Release 1 requirements (ITU-T
Rec. Y.2201), which are listed in section 8 of this
Specification.
1.5 This architecture for NGN does not restrict network
operators freedom to deploy
capabilities or use capabilities of their business partners.
Specific division of functional entities between the core and
access networks is based on operators business decisions rather
than hard points of separation in the architecture. Functional
entities may be mixed and matched in different ways. Physical
equipment may have both the core and the access network
functions.
1.6 Existing network operators may have adopted the overlay
approach in which
legacy networks like the Public Switched Telephone Network
(PSTN) / Integrated Service Digital Network (ISDN) and Public Land
Mobile Network (PLMN), will co-exist with the NGN for some time.
Therefore inter-working with PSTN/ISDN is an important
consideration in the architecture for NGN.
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2 Architecture for NGN 2.1 The architecture for NGN described in
this Reference Specification conforms to
the NGN architecture as shown in Figure 1, which is a 2-layered
NGN model, structured according to a service stratum and transport
stratum.
Figure 1: NGN Architecture Overview (ITU-T Y.2012) 2.2 The set
of functions within the transport stratum of the 2-layered NGN
model is
supported by many protocols which together compose the NGN
transport network. The end of the transport stratum protocol stack
is denoted by layer 3 of the Open Systems Interconnection (OSI)
Basic Reference Model (BRM) and the beginning of the service
stratum protocol stack is denoted by layer 4 of the OSI BRM (see
Figure 2). Layer 3 is the converging Internet Protocol (IP) layer
where the IP-based NGNs converge in providing IP connectivity
across the NGN transport network. Layer 4 is the Transmission
Control Protocol (TCP) or User Datagram Protocol (UDP) layer. A
variety of layer 1 (Physical layer) and layer 2 (Data Link layer)
will exist depending on the underlying technologies used to support
IP.
Figure 2: Generic Layered Protocol Stack Architecture 2.3 With a
flexible architecture for NGN which supports multiple access
network
technologies, a core network can be set apart from another core
network
Any Service & Every Service
Any Transport & Every Transport
Technology
Internet Protocol (IP)
Services Stratum
Transport Stratum
Scope of
NGN
Layer 7 Application Layer 6 Presentation Layer 5 SIP Layer 4
TCP/UDP Layer 3 IP layer Layers 2 & 1 Underlying technologies
that support IP e.g. SDH over Optical, Ethernet over Optical
Two Service Domains
NGN Strata View
Open Standards Interconnection (OSI)
Basic Reference Model View
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according to administrative needs or ownership. Access networks
can be set apart from core networks in that they do not provide
end-user services directly other than transport. Access networks
can be set apart according to technologies, administrative needs or
ownership.
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3 NGN Functions 3.1 Transport Layer Functions
The transport layer includes transport functions and transport
control functions.
3.1.1 Transport Functions 3.1.1.1 Transport functions provide
connectivity for all physically separated functions
within the NGN. These functions provide support for the transfer
of media information, as well as the transfer of control and
management information. Transport functions as defined in the ITU-T
Rec. Y.2012 include access network functions, edge functions, core
transport functions, gateway functions and media handling
functions.
3.1.1.2 No assumptions are made about either the technologies to
be used or the
internal structure, for example, the access transport network
and the core transport network.
(a) Access Transport Functions (Network Dependent)
NGN Release 1 supports access transport functions of diverse
technologies and capabilities. An access transport function
provides IP connectivity at the transport stratum, between the
end-user functions and the NGN core transport functions. The
following is a list of proposed technologies which implement the
access transport functions for the NGN Release 1:
xDSL: ADSL (ITU-T Recs. G.992.1, G.992.3 and G.992.5),
SHDSL (ITU-T Rec. G.991.2), and VDSL (ITU-T Recs. G.993.1 and
G.993.2) transport systems and supporting connection/multiplexing
technologies
SDH: SDH dedicated bandwidth access (ITU-T Rec. G.707) Optical
access: Point-to-point (IEEE 802.3ah 100Base-LX/BX), and
xPON transport systems such as BPON (ITU-T Recs. G.983 series),
GPON (ITU-T Recs. G.984 series), EPON (Gigabit EPON is sometimes
called GEPON), (IEEE 802.3ah 1000Base-PX)
Cable: Cable networks based on PacketCable multimedia
specifications as another type of access transport function (ITU-T
Rec. J.179)
LANs: LANs using either coaxial or twisted pair cable, including
10Base-T Ethernet (IEEE 802.3), Fast Ethernet (IEEE 802.3u),
Gigabit Ethernet (IEEE 802.3z), 10 Gigabit Ethernet (IEEE
802.3ae)
PLC: Power Line Carrier (PLC) networks transmitting and
receiving data over the power line
IEEE 802.X: Wireless networks (various publications for wireless
LAN and broadband wireless access)
3GPP IP-CAN: Mobile networks (IP connectivity access networks)
Broadcast: Broadcast networks (Internet broadcast/multicast,
DVB,
ISDB-T, various publications related to broadcasting)
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(b) NGN Core Transport Functions (Network Independent)
NGN core transport functions provide IP connectivity at the
transport stratum across the core network.
3.1.2 Transport Control Functions
Transport control functions include Resource and Admission
Control Functions and Network Attachment Control Functions.
3.1.2.1 Resource and Admission Control Functions (RACF)
(a) Within the NGN architecture, the Resource and Admission
Control
Functions (RACF) act as the arbitrator between Service Control
Functions and Transport Functions for QoS (ITU-T Rec. Y.1291)
related transport resource control within access and core networks.
The decision is based on transport subscription information,
Service Level Agreements (SLA), network policy rules, service
priority (defined by ITU-T Rec. Y.1571), and transport resource
status and utilization information.
(b) The RACF takes into account the capabilities of transport
networks and
associated transport subscription information for subscribers in
support of the transport resource control. The RACF interacts with
Network Attachment Control Functions (NACF), including network
access registration, authentication and authorization, parameters
configuration etc, for checking transport subscription
information.
(c) For delivering of those services across multiple providers
or operators,
SCF, RACF and Transport Functions may interact with the
corresponding functions in other NGNs. The details and other
aspects of the RACF are specified in ITU-T Rec. Y.2111.
3.1.2.2 Network Attachment Control Functions (NACF)
(a) The Network Attachment Control Functions (NACF) provide
registration at the access level and initialization of end-user
functions for accessing NGN services. These functions provide
transport layer level identification/authentication, manage the IP
address space of the access network, and authenticate access
sessions. These functions include:
Dynamic provisioning of IP addresses and other user
equipment
configuration parameters With endorsement of user,
auto-discovery of user equipment
capabilities and other parameters Authentication of end user and
network at the IP layer (and possibly
other layers) Authorization of network access based on user
profiles Access network configuration based on user profiles
Location management at the IP layer
(b) NACF includes Transport user profile which takes the form of
a functional
database representing the combination of a users information and
other control data into a single "user profile" function in the
transport layer. This functional database may be specified and
implemented as a set of cooperating databases with functionalities
residing in any part of the NGN.
3.2 Service Layer Functions
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Functional groups in the service layer include Service Control
Functions and Application Support and Service Support
Functions.
3.2.1 Service Control Functions 3.2.1.1 Service Control
Functions (SCF) include resource control, registration, and
authentication and authorization functions at the service level
for both mediated and non-mediated services. They can also include
functions for controlling media resources, i.e., specialized
resources and gateways at the service-signalling level.
3.2.1.2 SCF accommodates service user profiles which represent
the combination of
user information and other control data into a single user
profile function in the service layer in the form of functional
databases. These functional databases may be specified and
implemented as a set of cooperating databases with functionalities
residing in any part of the NGN.
3.2.2 Application Support Functions and Service Support
Functions
The Application Support functions and Service Support functions
include functions such as the gateway, registration, authentication
and authorization functions at the application level. These
functions are available to the Applications and End-User functional
groups. The Application Support functions and Service Support
functions work in conjunction with the Service Control Functions to
provide end-users and applications with the NGN services they
request.
3.3 End-User Functions 3.3.1 No assumptions are made about the
diverse end-user interfaces and end-user
networks that may be connected to the NGN access network.
End-user equipment may be either mobile or fixed.
3.3.2 NGN support for user functions is limited to the control
of user gateway functions
between the end user functions and the access transport
functions. The device implementing these gateway functions may be
customer or access transport provider managed. Management of
customer networks is however outside of the scope of the NGN
Release 1.
3.4 Management Functions 3.4.1 Support for management is
fundamental to the operation of the NGN. These
functions provide the ability to manage the NGN in order to
provide NGN services with the expected quality, security, and
reliability.
3.4.2 These functions are allocated in a distributed manner to
each functional entity
(FE), and they interact with network element (NE) management,
network management, and service management FEs. Further details of
the management functions, including their division into
administrative domains, can be found in ITU-T Rec. M.3060.
3.4.3 Management functions apply to the NGN service and
transport layers. For each
of these layers, they cover the following areas:
(a) Fault management (b) Configuration management (c) Accounting
management (d) Performance management
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(e) Security management 3.4.4 The accounting management
functions also include charging and accounting
functions (CAF). These interact with each other in the NGN to
collect accounting information, in order to provide the NGN service
provider with appropriate resource utilization data, enabling the
service provider to properly bill the users of the system. A
detailed description of the CAF functions can be found in 7.5/ITU-T
Rec. Y.2012.
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4 NGN Functional Entities
The NGN architecture given in Figure 1 is a service and
technology independent architecture which can be customised
according to services to be offered and technologies to be used. It
is a generalised NGN functional architecture where functional
entities (NGN FEs) are generic FE, which can become
technology-oriented according to context. Most of the NGN transport
layer functions (such as the RACF or NACF) will support different
types of NGN services in a common way. However, NGN implementations
need not implement certain transport layer functions such as
gateway FEs with respect to PSTN/ISDN, if they do not require the
support of such capabilities.
4.1 Transport processing FEs defined in 8.3.1/ITU-T Rec.
Y.2012:
T-1 Access Media Gateway Functional Entity (AMG-FE) T-2 Access
Node Functional Entity (AN-FE) T-3 Edge Node Functional Entity
(EN-FE) T-4 Access Relay Functional Entity (AR-FE) T-5 Access
Border Gateway Functional Entity (ABG-FE) T-6 Interconnection
Border Gateway Functional Entity (IBG-FE) T-7 Trunking Media
Gateway Functional Entity (TMG-FE) T-8 Media Resource Processing
Functional Entity (MRP-FE) T-9 Signalling Gateway Functional Entity
(SG-FE)
4.2 Transport control FEs defined in 8.3.2/ITU-T Rec. Y.2012:
T-10 Network Access Configuration Functional Entity (NAC-FE) T-11
Transport Authentication and Authorization Functional Entity
(TAA-FE) T-12 Transport User Profile Functional Entity (TUP-FE)
T-13 Transport Location Management Functional Entity (TLM-FE) T-14
Access Management Functional Entity (AM-FE) T-15 Home GateWay
Configuration Functional Entity (HGWC-FE) T-16 Policy Decision
Functional Entity (PD-FE) T-17 Transport Resource Control
Functional Entity (TRC-FE)
4.3 Service control FEs defined in 8.3.3/ITU-T Rec. Y.2012:
S-1 Serving Call Session Control Functional Entity (S-CSC-FE)
S-2 Proxy Call Session Control Functional Entity (P-CSC-FE) S-3
Interrogating Call Session Control Functional Entity (I-CSC-FE) S-4
Subscription Locator Functional Entity (SL-FE) S-5 Service User
Profile Functional Entity (SUP-FE) S-6 Service Authentication and
Authorization Functional Entity (SAA-FE) S-7 Interconnection Border
Gateway Control Functional Entity (IBC-FE) S-8 Access Gateway
Control Functional Entity (AGC-FE) S-9 Media Gateway Control
Functional Entity (MGC-FE) S-10 Breakout Gateway Control Functional
Entity (BGC-FE) S-11 User Signalling Interworking Functional Entity
(USIW-FE) S-12 Network Signalling Interworking Functional Entity
(NSIW-FE) S-13 Media Resource Control Functional Entity (MRC-FE)
S-14 Media Resource Broker Functional Entity (MRB-FE) S-15 General
Services Control Functional Entity (GSC-FE)
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4.4 Application Support and Service Support FEs defined in
8.3.4/ITU-T Rec. Y.2012:
A-1: Application Support Functional Entity (AS-FE) A-2:
Application Gateway Functional Entity (APL-GW-FE) A-3: Application
Service Coordination Manager Functional Entity (APL-SCM-FE) A-4:
Service Switching Functional Entity (SS-FE)
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5 NGN Service-specific Components 5.1 IP Multimedia Service
Component
The IP multimedia service (IMS) component provides mediated
services including the control and delivery of real-time
conversational services based on the re-use of the IMS. The IMS is
extended in NGN to support additional access network types such as
xDSL and WLAN. PSTN/ISDN simulation service is also provided by
this component. PSTN/ISDN simulation service refers to the
provision of PSTN/ISDN like services to advanced terminals such as
IP phones. The IMS component is specified further in ITU-T Rec.
Y.2021.
5.2 PSTN/ISDN Emulation Service Component
The PSTN/ISDN emulation (PES) service component enables the
support of legacy terminals connected through a gateway to an IP
network. All PSTN/ISDN services remain available and identical such
that end-users are unaware that they are not connected to a
TDM-based PSTN/ISDN. The PES component is specified further in
ITU-T Rec. Y.2031.
5.3 Other NGN Service Components
Other NGN service components will be defined in the future to
address other services such content delivery, multimedia multicast
or broadcast services, push services, data retrieval applications,
data communication services, online applications, sensor network
services, remote control services, and over-the-network device
management.
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6 Security Considerations
Security requirements within the functional requirements and
architecture of the NGN are addressed by the Security Requirements
for NGN Release 1 (ITU-T Rec. Y.2701). Security requirements are
voluntarily implemented by network operators or service providers
to protect their customers and the networks. NGN security is based
on a four layer conceptual model. (a) NGN security at the
application layer focuses on network-based
applications accessed by service providers customers.
Applications include web browsing, email, basic file transfer etc.
Security applied is to protect the customers and the networks.
(b) NGN security at the service layer addresses the security
concerns of the
services provided by service providers to their customers.
Services include domain name services, value-added services and
quality of service etc. Security applied is to protect the service
providers and their customers.
(c) NGN security at the IP layer addresses the packet flow which
is
supported by the network facilities in transporting information.
Security is focused on protecting the IP packets.
(d) NGN security at the data link layer focuses on protecting
the data frames
within a single link.
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7 NGN Release 1 Services 7.1 The NGN Release 1 provides an
extensible platform for services and an
architecture which is designed to be extensible, allowing new
services to be implemented as and when required. All services are
carried over the Internet Protocol (IP), which in turn may be
carried over a number of underlying technologies such as
Asynchronous Transfer Mode (ATM), Ethernet, etc. The functions
supported by the NGN Release 1 specifications are again illustrated
in Figure 3, which includes interfaces between NGN and end-user
functions, between NGN and other networks, and between NGN and
applications.
Figure 3: Transport and Service Configuration of the NGN (ITU-T
Y series Supplement 1)
7.2 The NGN Release 1 extensible platform and architecture
supports the following
services:
(a) Multimedia services (including PSTN/ISDN simulation
services); (b) PSTN/ISDN replacement support (emulation services);
(c) Data communication services; and (d) Public Interest Aspects
(for both multimedia services and PSTN/ISDN
replacement support) 7.3 The NGN Release 1 supports the
following functions:
a) Control of access and core transport networks (QoS, admission
control, authentication, etc.);
b) Co-ordination of multiple control components to a single core
transport network for resource control;
c) Inter-working and interoperability with legacy networks; d)
Mutual de-coupling of the application support functions from the
service
control functions and the transport layer; and e) Access
technology independence of service control functions and
application
support functions.
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7.4 Figure 3 represents the compilation of user and other
control data into two functions: "service user profile" and
"transport user profile" functions. These functions may be
specified and realised as a set of co-operating databases with
functionality residing in any part of the NGN.
7.5 End-user interfaces are supported by both physical and
functional (control)
interfaces. All categories of customer equipment are supported
in the NGN, from single-line legacy telephones to complex corporate
networks. Customer equipment may be both mobile and fixed.
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8 Capability Requirements for NGN Release 1 The high level
requirements and related capabilities for enabling the NGN Release
1 services (identified in ITU-T Y series Supplement 1) are defined
in ITU-T Rec. Y.2201. Selection of services to be included in any
specific network is a deployment decision of the operator. The list
of network capabilities for NGN is as follows: (a) Transport
connectivity (IPv4 and IPv6) (b) Communication modes (c) Media
resource management (d) Codecs (e) Access network and network
attachment (f) User networks (g) Interconnection, interoperability
and interworking (h) Routing (i) Quality of service (j) Accounting
and charging (k) Numbering, naming and addressing (l)
Identification, authentication and authorization (m) Security (n)
Mobility management (o) OAM (p) Survivability (q) Management (r)
Open service environment (s) Profile management (t) Policy
management (u) Service enablers (v) PSTN/ISDN emulation and
simulation (w) Public interest aspects (x) Critical infrastructure
protection (y) Non disclosure of information across NNI interfaces
(z) Inter-provider exchange of user-related information
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9 References Requirements given in this Specification are based
on the following reference
documents:
ITU-T Rec. Y.2012 (2006) Functional Requirements and
Architecture of the NGN
ITU-T Rec. Y.2201 (2006)
NGN Release 1 Requirements
ITU-T Series Y Supplement 1 (2006)
NGN Release 1 Scope
1 Scope2 Architecture for NGN3 NGN Functions4 NGN Functional
Entities5 NGN Service-specific Components6 Security Considerations7
NGN Release 1 Services8 Capability Requirements for NGN Release 19
References